<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">

    <title>Document</title>
    <style>
        .container {
            width: 100%;
            height: 100px;
            margin: 0;
            padding: 0;
        }

        .container ul li {
            float: left;
            list-style: none;
            font-size: 25px;
            background-color: pink;
        }

        @media screen and (max-width:767px) {
            .container {
                width: 100%;
            }

            .container ul li {
                width: 33.33%;
            }

        }
    </style>
</head>

<body>
    <div class="container">
        <ul>
            <li>导航栏</li>
            <li>导航栏</li>
            <li>导航栏</li>
            <li>导航栏</li>
            <li>导航栏</li>
            <li>导航栏</li>
            <li>导航栏</li>
            <li>导航栏</li>
        </ul>
    </div>
</body>

</html>